Batteries are widely used as rechargeable energy storage devices for a tremendous variety of different applications because of a battery's relative high energy and power density and relatively low cost in comparison to other storage technologies. Some such batteries are designed to be recharged. Among the available rechargeable battery technologies, the Lithium ion battery is very widely used and accepted due to its very high power and energy density. Lithium ion batteries find applications in portable electronics, hybrid and electric vehicles, renewable power systems and others. Such a battery is frequently discharged and re-charged.
The maximum charge level and the maximum charging rate for a lithium ion battery is often predefined by the battery manufacturer and accordingly the amplitude and duration of the charge being supplied to the battery (to recharge the battery) should be controlled. Generally, an electric charger is used for supplying a constant current and a constant voltage to reach a full charge that manufacturers specify. This known charging method uses a fixed charging profile in which a constant current is applied until a certain voltage is reached in the battery and then a constant voltage is applied to reach the full capacity. This is referred to as Constant Current/Constant Voltage charging (“CC/CV” charging). While this standard CC/CV charging profile is simple to implement in a battery management system, the known methods have not been completely optimized with respect to better performance, such as larger capacity storage, larger energy storage, shorter charging times, less cell degradation, better safety and so on.
There have been several approaches in the past to attempt to optimize the charging profiles. With “optimized” charging methods, charging speed has been improved. However, cell degradation caused by fast charging has not been taken into account in these known prior techniques. One of the significant issues is Lithium deposition, which occurs at the negative electrode during a fast charge, or at low temperatures (especially at the end of charging). During a rapid charge, lithium ions are transported from the cathode to the anode, which causes a high ion concentration at the anode surface because it takes a while for lithium ions to diffuse in the lattice structure and intercalate with the carbon atom structure. Lithium metal forms first near the electrode-separator boundary, where surface concentration of ions is at the highest during charging. When the lithium ions cannot insert themselves into a saturated negative electrode and they plate out of the electrolyte onto the surface, this leads to capacity losses of active lithium and of the electrolyte. This also compromises cell safety by creating the possibility for dendritic electrode growth that leads to an internal shorting-circuiting.
A major issue for a Lithium battery is a capacity fade during cycling, which is intensified by charging at high current. The reaction on the negative electrode is described asC6+xLi++xe−→LixC6  (1)
Primary side reaction taking place in anode is as follows, where the lithium ions react with electrons and form a lithium solid;Li++e−→Li(s)  (2)
Particularly, the side reaction described above increases as the current density becomes high and the cell is overcharged. A high current leads to a high lithium surface concentration between electrolytes and the negative electrode and causes excessive ions at the surface. These excessive ions cause side reactions and form lithium plating that eventually leads to aging and failures, particularly on the anode side. Therefore, the battery manufacturers specify a maximum charging current.
Accordingly, it can be seen that a need remains for a system and method for recharging batteries that allows the batteries to be rapidly recharged while minimizing deleterious effects, including a system and method for charging lithium ion batteries. It is to the provision of such that the present invention is primarily directed.